Known automation systems can include a multiplicity of field devices which communicate with one another and/or with superordinate control technology or a controller via a bus system. In this case, exemplary field devices can include drives, valves, motor protection and control devices, frequency converters, pressure and temperature measuring transducers, flowmeters and analysis devices.
Before an automation system is fit for use, the hardware can be modelled as part of a so-called project using a programming tool, also called an engineering tool. Information relating to input/output addresses of these hardware devices and their links to one another are configured in the project, for example.
In this case, the integration of the field devices in the automation system is based on standards, such as OPC, FDT (Field Device Tool), and on the field bus protocols and field bus specifications, for example FOUNDATION field bus or PROFIBUS.
When starting up or expanding a technical installation, field devices should be detected by the superordinate controller after they have been connected to the field bus of the automation system. This detection verifies access by the superordinate controller to the field devices of the automation system which is in the form of a programmable logic control system (PLC) or a process control system, in particular. For this purpose, the field devices are assigned unique bus addresses which can be used to address said field devices. The bus addresses are usually allocated from the superordinate position.
A specific identifier, the device address, which is used by the field device to register on the field bus is reserved for the respective field device for this purpose. The device address is preset in the field devices in the delivery state and can be stored in the memory of the field device but can also be set on the device using coding switches.
If a new field device is now connected to the network of the automation system, the field device initially can be addressed by the system using a so-called default address as part of the address allocation operation.
At present, the device addresses of the field devices should be taken into account when planning a field bus installation and should be matched to the subsequent actual situation in the field. For this purpose, the field device registers with the superordinate controller using the device address, which controller in turn allocates an individual bus address, which replaces the device address, to the device. The amount of planning and documentation needed in this case for the address allocation method is prone to errors and is time-consuming.
However, since the bus address allocated to the respective field device is needed only for protocol-specific communication with the device, for example in order to establish a connection between a controller and the field device or a superordinate control system (PLC) or a process control system and the field device, the bus address is of secondary importance to the user of the automation system since a special identifier or a system-specific name, also referred to as a “generic PD TAG”, can be used to identify the respective device inside the automation system.
In the process control system of a technical installation, the TAG comprises, for example, the position name of the respective field device in the system, which name can correspond to the measuring position number from an MCR (measurement/control/regulation) scheme and also comprises, inter alia, the respective function of the device, the manufacturer, the device type and its revision status.
Alternatively, there are tools on the market which detect the field devices, also referred to as bus users, connected to the bus with the aid of field bus communication and create the topology of the system from the data obtained in the process. However, this method works only if the field devices already have a suitable address for more unique identification, such as when the field bus has been started up.